"Fluorine has played a significant role in insect
control since about 1896 when sodium fluoride and various iron fluorides
were patented in England as insecticides. Sodium fluoride was used in the
United States for cockroach control before 1900 and was introduced in 1915
for the control of poultry lice. However, the use of fluorine insecticides
did not become general until the 1930´s when the disadvantages of arsenical
residues on food crops became apparent and the inorganic fluorine compounds
were introduced as safer substitutes. Systematic investigation of organofluorine
insecticides began about 1935 in the I. G. Farbenindustrie and the fluoroalcohols
and fluorophosphates (phosphorofluoridates) were intensively investigated
largely through the research of Schrader (1952). During World War II
fluoro-DDT or "Gix" was used for the control of insects of medical importance.
More recently, fluoroacetamide and analogues have been used as systemic
insecticides and a large variety of other fluorinated organic compounds have
shown insecticidal activity. Sulfuryl fluoride has recently been marketed
as a fumigant for household and structural pests..."

Alvord and Dietz, of Grasselli Chemical Company, Cleveland, Ohio, point out
certain problems with the use of soluble fluorides as insecticides (Ind.
Eng. Chem. 25 (June 1933) 629-633):

"The fact that sodium fluoride would control
certain types of insects had been known for many years, but all attempts
to use it and other fluorine compounds on plants failed because of plant
injury. Progress along the line of utilizing the fluorine compounds in this
connection really began with the discovery by Roark that the relatively insoluble
fluorides would not injure the foliage and would control certain insects.
About the time of this discovery, the Grasselli Chemical Company began to
experiment with barium fluosilicate. The development of this material was
held back for several years because of plant injury following its use, and
it was not until the discovery, quite by accident, that the injury was due
to an unsuspected impurity and that the pure compound was in reality safe
to most foliage, that rapid progress was made."

S. Marcovitch gives some details as to how those fluoride insecticdes work
(Ind. Eng. Chem. 16 (1924) 1249):

"The value of sodium fluosilicate as an insecticide
is due to the fact that it is both a contact and stomach poison. Shafer has
determined that when a roach walks over powdered sodium fluoride a little
of the powder adheres to the lower part of the body, antennae and tarsi of
the feet, and dissolves in the exudations of the integument. This seems to
cause some irritation and uneasiness; the insect soon begins to clean the
moistened powder from the body by licking it. In doing this enough of the
poison may be brought into the mouth and swallowed, to kill after a period
varying in from five to ten days. Other insects, such as Mexican bean beetles,
also have the habit of cleaning themselves and by putting their feet in their
mouths become very easy to kill. For this reason the sodium fluosilicate
is more effective against the adult beetles than the larvae, which do not
have these habits."

Because of such habits, toxicity to higher animals became of concern (Marcovitch
S.: "The fluosilicates as insecticides", Ind. Eng. Chem. 18 (June 1926) 572-573)

---

The Patents

1896

Charles Henry HIGBEE, of
New York City, N.Y.,
Manager of Manufacturing Company: "An improved composition
or material for destroying insects", British Patent GB 8236;
filed April 18, 1896; pat. May 23, 1896. ("The compounds
of fluorine which I employ for the purpose of destroying insects, are certain
soluble ones, viz.: sodium fluoride, ferric fluoride, the silico-fluorides
of the same bases, hydro-fluo-silicic acid, and the boro-fluo-silicates",
which the inventor claims to be less toxic for humans then many
of the compounds then in use for the same purpose, i.e. "arsenic, copper,
phosphorus, and the like")

1906

Karl
Heinrich WOLMAN and Bernard DIAMAND, Idaweiche, Oberschlesien, Germany,
assignors to Max Marschall, Nice-Cimiez, France: "Preserving composition
for fibrous material", US Patent 934,871; filed Nov. 6, 1906; granted Sept.
21, 1909 (uses "sodium fluorid" and "sodium
silico-fluorid". "We have also found that the salts of hydrofluoric acid
and of silicofluoric acid both of which are weak, bactericidal acids when
used in connection wioth a strong mineral acid, as above set forth, will
produce good results ...")

1908

Carleton
ELLIS, assignor, by mesne assignments, to Chadeloid
Chemical Company,
of New York, N.Y.: "Insecticide", US Patent 1,082,507; filed March 11, 1908;
pat. Dec. 30, 1913 ("The composition comprises a solution of wax in
carbon bisulfid, or similar penetrating organic liquid, emulsified with an
aqueous solution, considerably thickened for the purpose of emulsification,
and carrying in solution a powerful insecticide such as inorganic compounds
like bichlorid of mercury and ammonium fluorid, or organic compounds
like ammonium formate, etc.")

1911

Jacques WITTLIN, of Vienna,
Austria-Hungary, assignor of one-half to Siegfried Schlewinger, of New York:
"Antiseptic", US Patent 1,044,840; filed Jan. 12, 1911; granted Nov. 19,
1912 ("... my present invention further contemplates the
incorporation of ammonium fluorid or equivalent fluorin-containing salts
or fluorin compounds in the preparation of the antiseptic, whereby the
germicidal or disinfectant properties thereof are very materially
increased.")

1921

Henry Edward Percy
HUTCHINGS, of Barking Essex, UK: "Improvements in or relating to rat
and other vermin poisons", British Patent GB 187,424; filed Sept. 15, 1921;
pat. Oct. 26, 1922 (a bait for the purpose of rat and mouse
extermination, with additions of either sodium fluoride, barium carbonate,
squill or oxalic acid, to serve as a basic poison)

1923

Rurik C. ROARK, Baltimore, Md.: "Insecticide", US
Patent 1,524,884; filed Aug. 6, 1923; granted Feb. 3, 1925
("The poisonous action of soluble fluorides
is well known and has been utilized for the control of injurious insects.
For example, sodium fluoride, a salt readily soluble in water, is a very
effective roach poison and is a common ingredient of roach powders. Potassium
and barium fluorides have been similarly employed ...")

"There is nothing new in the use of sodium
fluosilicate as an insecticide. Its use for that purpose was described nearly
thirty years ago by HIGBEE (English Patent No. 8236, May 23, 1896). More
recently, WILLE has reported tests with sodium fluosilicate against roaches
and COBENZL mentions it as a common ingredient of rat and insect poisons"
(Roark C., Department of Agriculture: "Fluorides vs. fluosilicates as
insecticides", Science 63 (April 23, 1926) 431-2)

1926

Bernard GEHAUF
and Harold W. WALKER, of Edgewood, Md.:
"Method of making silicofluorides
and products thereof", US Patent 1,617,708;
filed May 14, 1926; pat. Feb. 15,1927 ("This
invention ... also comprises a new composition of matter
for insecticidal and other purposes ... made by neutralizing
hydrofluosilicic acid with the appropriate base ...
Hydrofluosilicic acid ordinarily is prepared by contacting
various waste gases containing silicon fluorid with
water.. Waste gases containing silicon fluorid arise in various
industries, as in the manufacture of
superphosphates.")

Martin J. FORSELL, Seattle,
Washington: "Insecticide", US Patent 1,618,702; filed Aug. 30, 1926; granted
Feb. 22, 1927 ("The insecticide consists of using apple after it is
dried and powdered and mixing therewith any well-known poison in powdered
form ... any one of the compounds of fluorine preferably sodium or potassium
fluoride or sodium or potassium silico fluoride ...)

Howard S. McQUAID, Cleveland,
Ohio, assignor to The Grasselli Chemical
Company, of Cleveland, Ohio: "Production of
Barium Silicofluoride"; US Patent 1,648,143; filed Nov. 22, 1926; patented
Nov. 8, 1927 (Process for production of barium
silicofluoride from sodium silicofluoride for use as an
insecticide)

Roscoe H. CARTER, Washington
D.C. (Government employee): "Process for the manufacture of insecticides
and method of making same", US Patent 1,842,443; filed
Nov. 15, 1929; granted Jan. 26, 1932 ("As pointed
out in other patent applications of mine, the double fluorides
of the alkali metals are useful insecticidal materials and can be formed
from water soluble salts of aluminum by
treatment with alkali metal compounds and
fluorine acids in the proper molecular proportions.")

1931

Arthur
H. HENNINGER, assignor to General
Chemical Company,
New York: "Process of making potassium aluminum fluoride", US Patent 1,937,956;
filed June 18, 1931; pat. Dec. 5, 1933 ("... for use as an
insecticide. It has heretofore been proposed to use potassium aluminum fluoride
as an insecticide for the control of various insect pests. This material
is considered to possess advantages over lead arsenate as an insecticide
for the reason that, although poisonous, the fluoride compound is less
toxic to human beings and animals than is lead arsenate.")

John E.
MORROW, assignor to Aluminum Company of
America: "Insecticide
and method of producing same", US Patent 2,210,594; filed Jan. 6, 1938; pat.
Aug. 6, 1940 ("Double fluorides of sodium and aluminum, such as natural
and synthetic cryolite, have been used as insecticides, and the usefulness
of such compounds as stomach poisons for various insects has been
established. It has been demonstrated, for example, that these fluorides
are particularly useful in combatting the codling moth and the Mexican bean
beetle.")

1948

Alan BELL, Kingsport, Tennessee, assignor
to Eastman Kodak
Company, Rochester, N.
Y.: "Insecticidal compositions comprising either hexyl alkyl tetraphosphate
or tetra-alkyl pyrophosphate and either an alkali metal fluoride or
fluorosilicate", US Patent 2,514,621; filed Dec. 26, 1948; granted July
11, 1950 ("Diethyl phosphate is the hydrolysis product
produced by most of these phosphorus insecticides such as organic
insecticides derived from triethyl phosphate - thionyl chloride reaction
product, hexaethyltetraphosphate, tetraethylpyrophosphate. This hydrolysis
product is not as toxic as parent compound in itself
but mixed with NaF or Na2SiF6 has
considerable toxicity.")